The parallel holes, the profiles of which are matched to those of the tubes which are to extend through them, are generally formed in press-formed elements or deformations by means of a piercing operation. In order to manufacture such a heat exchanger, it is necessary to start with a workpiece in the form of a pressing, which may also be referred to as a medallion. In a first step of the operation, this workpiece is press-formed using a first tool, in order to form a set of parallel press-formed elements.
A second stage of the operation is the piercing operation in which the holes are formed. One of these holes is formed in each of the press-formed elements of the workpiece. The forms and dimensions of the holes are matched to the transverse cross section of the tubes which are to be subsequently introduced into the holes. The press-forming operation of the first step in the process is only able to correspond to a single type of tube having preselected dimensions. In consequence, if it is desired to make a heat exchanger having tubes of dimensions which are substantially different from each other, it is necessary to take a fresh workpiece which is innocent of any deformations or press-formed elements, and then to form the latter by stamping with another press-forming tool, the press-formed elements being finally pierced to form the holes using another piercing tool which represents yet another tool.
Accordingly, there is therefore no standard type of header plate in existence that could be matched to the dimensions of tubes having different cross sections.
Consequently, one of the objects of the invention is to provide a header plate which does not have this drawback of the header plates in the prior art.